Corrosion resisting steel



Pa tented Aug. 1, 1933 UNITED STATES PATENT OFFICE William Herbert Keen,Albany, N. Y., assignor to Chas. W. Guttzeit, New York, N. Y.

No Drawing. Application July 10, 1928 Serial No. 291,697

17 Claims.

This invention relates to alloy steels and has for-an object to providea corrosion resisting steel.

Corrosion resisting steels have been produced heretofore containing 12%to 18% chromium but the cost of the same prohibits their usecommercially for structural beams and plates and in other applicationswhere the tonnage is high. I have discovered that the amount of chromiumand, therefore, the cost of the steel can be materially reduced ifmagnesium is present with the chromium. For example, in steelscontaining from 1.5% to 7.5 or more of chromium the presence ofmagnesium in amounts from 0.05%

to 2% or more adds -to the corrosion resisting properties more or lessin proportion to the amount of magnesium present.

The present invention has been developed more particularly in connectionwith the production of corrosion resisting steel suitable for use inboiler tubes, rolled plates, sheets and the like, such as used forroofing and in the manufacture of freight cars, and for convenience ofdisclosure such an embodiment of the invention will be described. Thedescription, however, is illustrative merely and it not intended asdefining the limits of the invention.

An alloy steel suitable for rolling and having corrosion resistingproperties may contain, for

Ordinarily the chromium may be kept between 4% and 7.5% to obtaindesiredquality without too great expense.

Manganese and silicon may be varied within the usual limits as inordinary or stainless types of .steel according to specification desiredwithout any marked effect upon corrosion resistance. Deoxidants such aszirconium; aluminum, calcium, boron and titanium may be used but are notessential to the quality of the steel.

' A steel of this character with chromium in the lower part of the rangeindicated while not necessarily having as effective corrosion resistingproperties as the best corrosion resisting chromium steel, willnevertheless withstand the effects of corrosion perhaps three or fourtimes as well as the steel now used for structural work and the like,and yet the cost will not be prohibitive.

(Cl. 75l) An increase of chromium improves the corrosion resistingproperties but adds to the expense. Such elements as vanadium,molybdenum, tungsten or tantalum may be advantageously added for theusual purposes and do not substantially change the corrosion resistingproperties of this steel.

The addition of magnesium to corrosion resistingsteels of higherchromium content is also beneficial and improves their stain resistingproperties to a noticeable degree. This improvement is especiallynoticeable in improved resistance to attack of acetic acid, and is alsoapparent on the copper sulphate test which is now being employed by manyusers of steels of this type. Benefits are noted even with very smallamounts such as are barely determinable by chemical analysis, but aremore marked with increasing quantities on up to 1.5% and 2%.

In the manufacture of this steel the alloys should in general be addedin the usual manner, but it is desirable that the magnesium be addedshortly before pouring when the steel has been properly killed and thetemperature is about right for tapping. A small area of the bath shouldbe cleaned of slag by means. of a scraper and the magnesium addeddirectly to the metal. Tapping should follow as soon as practicable toavoid undue loss of magnesium. Ordinarily the addition of pure magnesiummetal is impractical. The ideal alloy to be added would be a compositionof magnesium and iron, but up to the present time no one has been ableto produce a ferro-magnesium alloy. Nickel magnesium is perhaps the mosteasily obtained and generally the most desirable alloy to add inpractice. However, some of the more common alloys such asaluminum-silicon-magnesium, aluminum-magnesium, ormagnsium-manganese-silicon may eiiectively be added. The use of acompound containing aluminum has the advantage that the presence ofaluminum also improves the corrosion resisting properties and permits areduction of the percentage of magnesium to obtain the same degree ofcorrosion resistance. A mixture of several alloys may be added, ifdesired.

It is of interest to note that steel of the character described wi..'withstand exposure over long periods at elevated temperatures. At 1700Fahrenheit, for instance, there is no appreciable oxidation.

The steel described may be readily rolled into structural shapes,plates, sheets and the like, and it can be produced at a cost which ismore than justified by the greater durability.

The following analyses of typical steels which have been found suitablefor rolling into plates, sheets, and the like, are illustrative- It willbe noted that in these typical steels, the chromium approximates 5% andis within the range of 3.5% to 5.5%, and the magnesium ap proximates 1%and is within the range of 0.5%

to 1.5%. These analyses are illustrative merely of steels which wouldmeet the physical requirements for tonnage applications.

A fairly good degree of hardness is obtainable if desired even in thelower range of carbon as illustrated by a steel of the followingcomposition: carbon .44%, chromium 4.89%, magnesium .12% and nickel1.41%. When hardened by quenching in oil, a Brinell hardness may beobtained as shown below:

v The addition of the magnesium apparently does not cause a depreciationin the hardening quality as does the addition of some other elements,as, for example, aluminum, but an effect similar to the effect ofaluminum would be reasonable to expect if the magnesium content werefurther increased.

I claim:

1. A corrosion resisting steel containing 1.5% to 20% chromium, and 0.5%to 2% magnesium, the remainder being substantially iron.

2. A corrosion resisting steel containing 3.5% to 20% chromium, and 0.1%to 2.5% magnesium, the remainder being substantially iron.

3. A corrosion resisting steel comprising approximately 5% chromium andapproximately 1% magnesium, the reminder being substantially iron.

4. A corrosion resisting steel comprising approximately 3.5% to 5.5%chromium and approximately 0.5% to 1.5% magnesium, the remainder beingsubstantially iron.

5. A corrosion resisting steel comprising approximately 5% chromium andapproximately 1% magnesium, together with approximately 1% aluminum, theremainder being substantially iron.

6. A corrosion resisting steel comprising approximately 3.5% to 5.5%chromium and approximately 0.5% to 1.5% magnesium, together with anappreciable amount, more than an impurity, aluminum ranging up to 2%,the remainder being substantially iron.

7. A corrosion resisting steel containing 1.5% to 20% chromium and 1% to5% magnesium, the remainder being substantially iron.

8. A corrosion resisting steel comprising approximately 5% to 9%chromium and .10% to 5.0% magnesium, the remainder being substantiallyiron.

9. A corrosion resisting steel containing 3% to 20% chromium to cause asubstantial resistance to corrosion and 0.15% to 5% magnesium tosubstantially increase the corrosion resistance, the remainder beingsubstantially iron.

10. A corrosion resisting steel comprising approximately 3.5% to 5%chromium and approximately 0.5% to 5% magnesium, the remainder beingsubstantially iron.

11. A corrosion resisting steel comprising approximately 3.5% to 7%chromium and approximately 0.15% to 5% magnesium, the remainder beingsubstantially iron.

12. A corrosion resisting steel comprising approximately 5 to 9%chromium and 1 to 5% magnesium, the remainder being substantially iron.

13. A corrosion resisting steel comprising 3.5 to 20% chromium and l to5% magnesium, the remainder being substantially iron.

14. A corrosion resisting steel comprising 3.5 to 5.5% chromium and 1 to5% magnesium, the remainder being substantially iron.

15. A corrosion resisting steel comprising 3.5 to 5.5% chromium and l to2.5% magnesium, the 120 remainder being substantially iron.

16. A corrosion resisting steel comprising 3.5 to 7.5% chromium and 0.25to 0.75% magnesium, the remainder being substantially iron.

17. A corrosion resisting steel comprising 5 125 to 7% chromium and 0.25to 0.75% magnesium, the remainder being substantially iron.

WILLIAM HERBERT KEEN.

